Method of forming glass fibers



Nov. 8, 1966 G. E. EILERMAN 3,284,179

METHOD OF FORMING GLASS FIBERS Filed Jan. 2, 1963 INVENTOR. 6t0k6 2 [/ZfRNA/V United States Patent P 3,284,179 METHOD OF FORMING GLASS FIBERS George E. Eilerman, Pittsburgh, Pa., assignor to Pittsburgh Plate Glass Company, Pittsburgh, Pa, a corporation of Pennsylvania Filed Jan. 2, 1963, Ser. No. 249,066 5 Claims. (Cl. 653) This application is a continuation-in-part of my appli cation Serial No. 810,765, filed May 4, 1959, now abandoned, which application is in turn a continuation-inpart of my application Serial No. 631,012, filed December 28, 1956, now abandoned.

Thc'present invention relates to an improved method of forming glass fibers and it has particular relation to a method of sizing glass fiber textiles during their formation so that the glass fiber textiles have improved processing and tensile strength characteristics.

A glass fiber strand is composed of a multitude of fine glass filaments. The strand is formed by drawing glass at a very high rate of speed, i.e., 500 to 20,000 feet per minute through small orifices in an electrically heated, platinum-rhodium alloy bushing to form filaments, gathering the individual filaments into the strand and winding the strand on a forming tube such as is shown in US. Patent No. 2,133,238. After formation of the strand, it is unwound from the forming tube and fabricated into yarn. A single glass fiber strand may be twisted and used as yarn or it may be twisted and plied with other glass fiber strands or textile threads to form yarn.

It can be seen that in the formation of the yarn there are several steps in which the glass fiber strand is wound upon and unwound from a tubular support. It is essential that the strands retain their integrity in these winding and unwinding operations for efiicient yarn production. During formation of the strand, the individual glass filaments are coated with a size which acts as a binder to bind the filaments together and provide the strand with integrity for twisting, plying and weaving. The size also serves as a lubricant for the filaments to prevent destruction of the strand by abrasion of the individual filaments against each other and against the equipment upon which it is fabricated. If the strand does not have proper integrity and the filaments are not properly lubricated, the filaments break and accumulate at some point on the fabricating equipment, fuzzing occurs and eventually the strand breaks.

At present, textile sizes for glass fibers are made with starch as a binder. Starch has been found to be desirable for it is water dispersible and therefore can be applied from an aqueous system. Furthermore, starch is inexpensive compared to other binding materials.

The starch sizes are usually compounded with other materials such as wetting agents and softening agents which are beneficial for fabrication of the sized yarn. The wetting agent enables the binder and other ingredients of the size to wet the glass surface and adhere to it more readily. This permits the accomplishment of a more uniform coating of the size on the glass surface. The softening agent or lubricant, which may be or may include an oil, provides the size with the property of release which enables a sized strand to be unwound from a package. It also enables the strand or yarn to slide through and over fabricating elements such as a traverse or guide without breaking any of the individual filaments.

The incorporation of oils and materials which are not easily dispersible in an aqueous size places certain re- 3,284,179 Patented Nov. 8, 1966 straints upon the application of the size. It is desired to apply the size in an aqueous medium. An oil must be emulsified in water to permit its uniform application to the fibers. When any appreciable amount of oil is employed as an emulsion in the size, the 'viscosity of the size is unduly increased. In order to maintain these aqueous sizes at the proper viscosity for satisfactory application to the individual filaments, the sizes must be heated and applied to the glass fibers at an elevated temperature, i.e., to F. It can be seen, therefore, that it is desirable that a starch size be formulated which can be applied at room temperature and at the proper viscosity.

A further disadvantage to the starch sizes presently employed with oils as softening agents is that the solids contentof the size must be kept relatively low in order to provide the size with the proper viscosity for application to the fibers. It is desired that the size have a relatively high solids content so that the tensile strength of the glass fiber strand is as high as possible. The viscosity characteristics of the starch-oil size presently employed do not permit the presence of a high percentage of solids in the size and this limits the tensile strength which can be ultimately obtained in the glass fiber yarn. The maximum solids content of starch sized yarns which can be successfully fabricated at present is about 12 to 15 percent by weight of the size. It is therefore a desideratum of the art to formulate a starch size having higher permissible binder solids content at the desired viscosity for application to the fibers. Another object of the present invention is to provide a starch size which does not contain an oil.

In general, there are two methods of applying sizes to glass fibers. One method involves gathering the individual filaments together and passing them over a wool pad which is saturated with the size. Another method involves passing the individual filaments over a rotating surface which is flooded with the size and thereafter gathering the coated filaments into a strand. The rotating surface can be cylindrical, e.g., a roller surface, or elliptical, e.g., a continuous belt or band surface. The physical loss of size when applied by means of the pad is about twice that observed in the use of the roller or continuous belt applicators. Also, the individual filaments are more efficiently coated with the roller or continuous belt applicators. Thus, it is desired to use an applicator of the rotating surface type whenever possible.

Many of the presently known starch containing sizes must be applied to the glass fibers by means of a pad applicator. As stated above, the presently used oil-containing starch sizes must be heated to provide them with the proper viscosity for application. At these temperatures, the oil phase in the starch size is unstable. It separates from the size and accumulates on the roller or continuous belt. This results in a change of the chemical composition of the size on the glass fibers and is undesirable. The strand which is provided with the starch-oil size by means of a roller applicator has been observed to break more frequently in subsequent fabricating operations. Thus, it is an object of the present invention to formulate a starch size which can be effectively applied by means of an applicator of the rotating surface type, e.g., a roller applicator or continuous belt applicator.

A further disadvantage of the use of starch as a size for glass fibers is that the sized glass fiber-s must be twisted and plied very shortly after the size has been applied to the fibers, i.e., one or two days thereafter. After several days, the water evaporates from a starch size and the continuous film on the fibers and between the fibers is destroyed. The integrity of the strand is thereby lost and the strand tends to fuzz badly during twisting and plying. It is therefore desired that a starch size 'be provided for glass fibers which enables the fibers to be stored for periods of time longer than several days prior to being twisted and plied in the formation of yarn. Such a glass fiber size permits the establishment of a strand or yarn inventory and thereby permits greater flexibility in the twisting and plying portions of the manufacturing process.

In accordance with the present invention, an improved method of producing glass fiber yarn has been provided in which a size is applied to the fibers during their formation to give better strand integrity .and higher tensile strength to the sized yarn. The size is applied to the glass fibers at room temperature by efficient methods. The size permits the yarn to be fabricated without fuzzing after being stored over long periods of time.

The size employed in the present invention contains a combination of starch and a synthetic latex as the binder. The latex contains a relatively high content of solids at a low viscosity and the ratio of starch to latex in the size can vary over a wide range and still remain within the required limits of viscosity for application to glass fibers moving at high rates of speed. Sizes containing as high as 20 to 25 percent solids have been successfully applied to glass fiber yarn in standard production. The strand integrity and tensile strength of yarn sized with such high solids material is improved.

The combination of a latex with the starch in the size permits room temperature application of a starch containing size. The compounding of such a size has been improved to the point where oil can be omitted from the size and the size can be applied by a roller applicator rather than the conventional pad. The combination of starch and the latex in a size provides a glass fiber strand that can be processed through more textile operations with a minimum of broken filaments. This is especially true of larger filament yarns such as 75 1/0 yarns and the heavier yarns such as 75 1/ 2 yarns where more tension is required in fabrication of the yarn.

At the present time, prior art starch sized, la-r-ger filament strands can be fabricated on a twister tube from a forming pack-age. Any subsequent fabrication such as cone winding destroys the strand integrity of the sized yarn and causes a certain amount of broken filaments. With the size employed in this invention, further textile operations can be performed on the yarn with good strand integrity still in evidence and with few, if any, filaments being broken.

In addition to starch and latex, the size should contain a wetting agent and a softening agent or lubricant. The size may also contain conventional oil-free finish materials or coupling agents for rendering the glass fiber surfaces moisture resistant and compatible with resins.

The method of the present invention is illustrated in the drawing. The size is applied at room temperature to the individual filaments 11 just after their emergence from the electrically heated platinum-rhodium alloy bushing 13 and prior to or at the same time they are grouped together by guide 15 to form the strand. The size may be applied by means of a roller or belt applicator 17 such as shown in US. Patents Nos. 2,728,972 and 2,873,718. The fibers, in their formation, are preferably drawn at speeds of about 10,000 to 12,000 feet per minute and wound around a forming tube 20. A traverse 21 directs the strand in open wind onto the tube 20. For successful application of the size at these speeds of glass fiber travel, the size should have a viscosity of less than 100 centipoises at C. and preferably 1 to 20 centipoises at 20 C. The glass fibers thus formed are dried at room temperature for about 15 hours.

Typical examples of the sizes of the present invention are as follows:

Example I Per-cent by weight Starch 2.4 Polyvinyl acetate latex (55% solids latex contains a wetting agent as manufactured) 22.4 Dibutyl phthalate (plasticizer for polyvinyl acetate) 4.5 Cation X (softener) 1.1 Water 69.6

Example II Starch 9.8 Polyvinyl acetate latex (55% solids) 12.5 Dibutyl phthalate 2.5 Zinc stearate 1.3

Tween 61 (wetting agent-a polyoxyethylene sorbitan mono-stearate) 0.2 Water 73.7

Example III Starch 13.0 Polyacrylate latex (46% solids) 7.0

Rhotex 200 (50% solidsplasticizer, an oil modified sebacic acid alkyd resin) 1.3 Zinc stearate 1.3 Tween 81 (wetting agent-a polyoxyethylene sorbitan tri-oleate) 0.7

Water 7 6.7

Example IV Starch 10.3 Polyvinyl acetate latex (55 solids) 9.9 Zinc stearate 0.8 Cation X (softener) 0.4 Avcosol 104 (softenera mixture of polyalkylene oxide derivatives of a polyhydric alcohol, fatty acid ester) 0.2 Stearic acid-chromie chloride complex (Quilon) 1.3 Arquad S (wetting agent) 0.1 Water 77.0

Example V I Starch 7.6 Polyvinyl acetate latex (55% solids) 8.5 Dibutyl phthalate 1.7 Cation X (softener) 0.8 Zinc stearate 0.5 Stearic acidchromic chloride complex (Quilon) 0.9 Arquad S (wetting agent) 0.2 Water 79.8

Example VI Starch 7.6 Polyvinyl acetate latex (55 by weight solids) 8.5 Dibutyl phthalate 1.7 Vinyltriacetoxy silane 0.7 Zinc stearate 0.5 Cation X (softener) 0.8 ArquadS (wetting agent) 0.2 Water 80.0

The preparation of the size listed in Example V may be described as being illustrative of the method of preparing the sizes of the present invention. This size can be made by making about 150 gallons of a hot to F.) solution of Cation X (an acylated imidazoline which is formed as a reaction product of stearic acid and tetraethylene pentamine) and an aqueous solution of Arquad S (alkyl trimethyl ammonium chloride wherein the alkyl groups are composed of 10 percent by weight octadecyl, 35 percent by weight octadecenyl, 10 percent chloride.

by weight hexadecyl and 45 percent by weight octadecadecenyl). Zinc stearate is added to the hot aqueous solution and the mixture is agitated until the zinc stearate is thoroughly dispersed therein.

After the zinc stearate is thoroughly dispersed in the aqueous solution, the temperature of the mixture is raised to about 180 F. and the starch is added. The mixture is held at this temperature for minutes and then cooled to 90 F. The stearic acid-chromic chloride complex is then added. The polyvinyl acetate dispersion is next added to the mixture and water is added to provide the proper percent solids to the dispersion. The pH of the sizing solution is about 4.7 plus or minus 0.3. The above procedure is exemplary and it is contemplated that the various oil-free adjuvant materials, such as wetting agents and softening or lubricating agents and other additional finishing materials may be added in other sequence.

The preferred class of synthetic resin latices are latices containing homopolymers prepared by the homopolymerization of monoolefinically unsaturated monomers, with polyvinyl acetate latex being by far the preferred homopolymen'c synthetic resin latex.

.Although polyvinyl acetate is preferred for use as a latex, other homopolymeric latices similar to polyvinyl acetate can be added to starch sizes to improve the application of sizes to glass fibers and to improve the fabrication and tensile strength properties of glass fibers sized with such material. Numerous polar and non-polar homopolymeri-c latices which function as glass fiber binders can be combined with the starch. These binders are latices, i.e., aqueous dispersions of synthetic resins made by an aqueous emulsion homopolymerization of ethylenic monomers, various acrylates which are esters of acrylic or methacrylic acid and an aliphatic alcohol having 1 to 6 carbon atoms including, for example, methyl methacrylate and methyl acrylate, vinyl chloride, styrene, acrylonitrile, chlorovinyl acetate, and vinylidine Moreover, mixtures of any two or more of the above-mentioned homopolymers can be employed as the synthetic resin latex component in accordance with this invention. When such mixtures of homopolymers are employed, they can contain advantageously significant amounts of polyvinyl acetate, e.g., 50 to about 80 percent by weight polyvinyl acetate.

While homopolymeric latices are the preferred class of synthetic resin latices for most purposes, it is sometimes desirable and even advantageous to employ copolymeric latices prepared by copolymerization of butadiene with either styrene or acrylonitrile either in place of or in admixture with the homopolyrneric latex. An aqueous system is usually employed to deposit the size on the glass fibers when the butadiene styrene or butadiene acrylouitrile copolymeric latices are combined with starch. Water is also preferred as the solvent or dispersion medium when homopolymeric latices are combined with starch.

The synthetic resin latices generally have an average particle size of 0.1 to 5 microns.

The starch component of the size can be any of the natural starches, e.g., corn starch, wheat starch, rice starch, potato starch, or dextrinized starches prepared from any one of the above-mentioned natural starches. All of these starches are hydrophilic colloids exhibiting hydrophilic tendencies to varying extents. Especially good results are secured using dextrinized corn starch, and dextrinized corn starch was employed as the starch component in the aqueous glass fiber sizing composition of Examples I to VI above.

A plasticizer is used in the size with latices which tend to deposit as a brittle or discontinuous film. For example, a plasticizer is generally used with latices of polyvinyl acetate, polyvinyl chloride, the polyacrylates and polystyrene, whereas a plasticizer is not generally used with a butadiene-styrene latex. The plasticizer may be any known plasticizerfor the various latices, such as dibutyl phthlate, tricresyl phosphate, dioctyl phthalate, diisooctyl phthalate and other esters which are conventionally used as plasticizers.

Various amounts of starch and latex binder may be present in the size. The starch solids may constitute 2 to 15 percent by weight of the size and the latex solids may constitute 2 to 15 percent by weight of the size. In all events, the amount of starch and latex binder. employed should not exceed that amount for each constituent which will cause the viscosity of the solution to be greater thanabout centipoises at 20 C. Solutions having viscosities greater than 100 centipoises at 20 C. are very diflicult to apply to glass fiber strands due to the very high speeds of fiber travel during attenuation and forming of the strand. It is preferred that the viscosity of the size be between 1 and 20 centipoises at 20 C. for best results.

The minimum weight ratio of latex to starch is about 1 to 7 parts by weight. The maximum weight ratio of latex to starch if zinc stearate is not present in the size is about 7 to 1. When zinc stearate is present, the ratio of latex to starch maybe increased to the point where no starch is present in accordance with the teaching of my copending application Serial No. 734,828, filed May 13, 1958. The total starch and latex solids in the size may be 10 to 18 percent by weight. The pH of the size may vary from about 3 to 8 depending upon the sensitivity of the latex to precipitate from the dispersion. The more resistant the latex is to precipitations, the higher the pH of the sizing solution.

The amount of size which is applied to a glass fiber strand to achieve binding of the individual filaments to each other throughout their entire length or substantially their entire length is limited by the method of forming the strands. The solids content of the size is about 13 to 20 percent by weight. The high speed of forming permits the application of about 3 to 8 percent by Weight of solid binder on the strand. Greater amounts of binder are desired to increase the tensile strength of the yarn, however, if too much binder is present on the yarn, fabrication difficulties such as difiiculty in unwinding the sized yarn are encountered.

A cationic-active substance such as a. cationic oilfree wetting agent is generally employed in the size. Suitable wetting agents include cetyl or stearyl monoamine hydrochloride or acetate, dodecylamine, hexadecylamine and secondary and tertiary derivatives of the same, for example, dodecyl methylamine and salts thereof. Alkyl imidazoline derivatives such as described in US. Patents Nos. 2,200,815; 2,267,965; 2,268,273 and 2,355,837 are also satisfactory. Quaternary ammonium compounds such as trimethyl stearyl or cetyl ammonium bromides and chlorides and generally any of the amine compounds that dissociate in water systems to provide a positive radical containing a group of more than 8 and preferably 12 or more carbon atoms may be used.

Non-ionic oilfree wetting agents may also be used. They are not as active as cationic wetting agents and therefore must be used in greater amounts to provide the same degree of wetting. Examples of suitable nonionic wetting agents include polyalkylene oxide derivatives of esters, fatty acids, fatty alcohols, fatty amides, alkyl phenyl ethers and many other derivatives.

The latex, as manufactured, contains an oil-free wetting agent. Sometimes the wetting agent present in the latex is sufficient to lower the surface tension of the size to a degree where no additional wetting agent need be added to the size. In any event, the amount of wetting agent employed generally ranges from about 3 to 40 percent by weight of the solid binder employed in the size or 0.01 to 1 percent by weight of the size.

An oil-free softener should be included in the size. Some of the above listed materials function as both wetting agents and softeners in the size. For example, some alkyl imidazoline derivatives such as the reaction product of stearic acid, tetraethylene pentamine and acetic acid function as softeners as well as wetting agents. Avcosol 104 functions in the same manner. Zinc stearate performs as a softener and a release agent. The stearic acid-chromic chloride complex (Quilon) may function as both a softener and a finish material. Cation X is a softener. An acid solubilized water dispersible stearic amide, an anhydrous acid solubilized, water dispersible, lower molecular weight, fatty acid amide and an anhydrous acid solubilized polyunsaturated, lower molecular weight, fatty acid amide may be used as softeners. The amount of softener generally ranges from about 1 to 25 percent by weight of solid binder in the size or about 0.05 to 2 percent by weight of the size.

The aqueous solutions of starch and latex set forth above may have added thereto, any one of a number of oil-free finish materials suitable for providing moisture resistance to glass fibers or acting as coupling agents for improving surface characteristics of glass fibers for laminating with various resins. In addition to the chromic chloride complex of stearic acid as set forth in Examples IV and V, other complex compounds of the Werner type in which a trivalent nuclear chromium atom is coordinated with acyclic carboxylic acido groups having 3 to 20 carbon atoms such as methacrylic, acrylic, crotonic, furoic, furfural-acrylic, and sorbic acids and all the unsaturated acids derived from linseed oil and from oiticica oil and other unsaturated acids in which the unsaturation is in the alpha to beta position may be employed. Examples of such compositions are set forth in US. Patents Nos. 2,552,910 and 2,611,718.

The invention is also practiced in combination with the use of various silane and siloxane materials suitable for improving the surface properties of .glass fibers for resin reinforcement. For example, vinyl and allyl, halo, alkoxy, or acyloxysilanes, their hydrolysis products and polymers of the hydrolysis products are suitable for improving the surface properties of the glass fibers. Some if these silanes are disclosed in U.S. Patents Nos. 2,563,- 288; 2,688,006; 2,688,007; 2,723,211; 2,742,378; 2,754,- 237; 2,776,910 and 2,799,598. Other coupling agents include the reaction products of vinyltrichlorosilane and organic acids and acid derivatives thereof, such as acetic acid, stearic acid, acrylic acid, formic acid, propionic acid, butyric acid, monoesters of dibasic acids such as the monoalkyl esters of maleic, citraconic and itaconic acids, etc. Amino silanes such as gamma-amino-p-ropyl triethoxy silanes may be used when the resin to be reinforced is an epoxy resin. The amount of finish material is usually between 0.5 and 25 percent by weight of solid binder in the size or about 0.1 to 2 percent by weight of the size.

The invention is particularly useful when the glass fiber yarn is to "be used as a reinforcement for paper. The yarn is employed as a woven or unwoven fabric between two or more plies of paper. Usually the yarn is employed as single ends in parallel relationship to each other throughout the paper.

Glass fiber yarn which has been sized according to the method of the present invention is also particularly useful as a yarn which may be coated with various types of thermoplastic resinous materials such as vinyl plastisols, e.g., solvent solutions of polyvinyl chloride, or other plastisols. Good adhesion is obtained between the yarn and the resinous material. The resin coated yarn is particularly useful for making insect screening, awnings, braided sleeving on wire and other uses where high tensile strength, weatherability, adhesion and other properties provided by such coated yarn are desired.

The invention may also be utilized when the glass fibers are to be used for making glass fabrics for decorative and other purposes and when they are to be used as a reinforcement for low pressure thermosetting-type resins, for x pl IlSfiturated polyester ethylenic monomers such as shown in US. Patent No. 2,676,947 granted to Parker. These resins are interpolymers of (A) a polyester of (1) a dihydric alcohol such as ethylene glycol, propylene glycol, 1,3-b utylene glycol, diethylene glycol, dipropylene glycol and higher polymers of alkylene glycols, and (2) an alpha, beta ethylenic dicarboxylic acid such as maleic or fumaric acid with other dicarboxylic acids such as adipic, succinic, azelaic, and phthalic acids being added, and (B) a monomer, soluble in the polyester, containing a terminal ethylenic group, CH such as styrene, vinyl acetate, vinyl toluene, allyl esters including allyl acetate, allyl succinate, diallyl phthalate, diallyl cyanurate, triallyl cyanurate, dichloro styrene, etc. The invention is also useful when the glass fibers are to be laminated with other resinous or plastic materials such as polyethers or epoxy resins. These resins are condensation polymers of an epihalohydrin, e.g., epichlorohydrin, and polyhydroxy phenolic compounds and derivatives thereof, such as bisphenol A, which is 2,2-bis(parahydroxyphenyDpropane.

The size composed of starch and latex has improved application properties over presently known starch sizes. It can be applied at room temperature from a stable aqueous solution by means of a roller applicator at the proper viscosity for high speed coating. The sized strands or yarn can be stored for long periods of time for further fabrication. The .glass fiber textiles have improved integrity and tensile strength and adhere better to a wide variety of resinous materials.

Although the present invention 'has been described with respect to specific details of certain embodiments thereof, it is not intended that such details act as limitations upon the scope of the invention except insofar as set forth in the accompanying claims.

I claim:

ll. A method which comprises drawing glass filaments from a molten supply of glass at a high rate of speed, gathering the filaments and combining them into a strand and applying an aqueous size to the filaments as they are being drawn, said size consisting essentially of an aqueous dispersion containing 2 to 15 percent by weight of starch and 2 to 15 percent by weight of a synthetic resin latex selected from the group consisting of:

(A) homopolymers of vinyl acetate, methyl methacrylate, methyl acrylate, vinyl chloride, styrene, acrylonitrile, chlorovinyl acetate and vinylidine chloride;

(B) homopolymeric mixtures containing at least tWo of the homopolymers of (A); (C) copolymers of 'butadiene with a monomer selected from the group consisting of: (l) styrene, and (2) acrylonitrile; (D) polymeric mixtures of a homopolymer of (A) and a copolymer of (C); and (E) polymeric mixtures of a mixture of homopolymers of (B) and a copolymer of (C), the combined weight of the starch and latex solids plus a small, effective amount of an oil-free, textile softener constituting about 13 to 20 percent by weight of the size, said solids, softener and water being the essential ingredients of the size, said size having a viscosity of about 1 to 20 centipoises at 20 C. I

2. The process as described in claim 1 wherein the size contains 0.01 to 1 percent by weight of a Wetting agent and 0.5 to 2 percent by weight of a textile softener.

3. The method as described in claim 1 wherein the latex is polyvinyl acetate.

4. The method as described in claim 2 wherein the latex is polyvinyl acetate.

5. A method which comprises drawing glass filaments from a molten supply of glass at a high rate of speed, gathering the filaments and combining them into a strand and applying an aqueous size to the filaments as they are being drawn by contacting the filaments with a moving surface coated with the size, said size consisting essentially of an aqueous dispersion at room temperature containing 2 to 15 percent by weight of starch and 2 to 15 percent by weight of a synthetic resin latex selected from the group consisting of:

(A) homopolyrners of vinyl acetate, methyl met-hacrylate, methyl acrylate, vinyl chloride, styrene, acrylonitrile, chlorovinyl acetate and vinylidine chloride; (B) =homopolymeric mixtures containing at least two of the homopolyrners of (A); (C) copolymers of butadiene with a monomer selected from the group consisting of: (1) styrene, and (2) acrylonitrile; (D) polymeric mixtures of a homopolymer of (A) and a copolymer of (C); and (E) polymeric mixtures of a mixture of homopolymers of (B) and a copolymer of (C),

References Cited by the Examiner UNITED STATES PATENTS 5/ 1956 Mennerich OTHER REFERENCES Inorganic Fibres, London, National Trade Press Limited, 1958, pages 36-40.

l6l-265 X EARL M. BERGERT, Primary Examiner.

P. R. WYLIE, Assistant Examiner. 

1. A METHOD WHICH COMPRISES DRAWING GLASS FILAMENTS FROM A MOLTEN SUPPLY OF GLASS AT A HIGH RATE OFSPEED, GATHERING THE FILAMENTS AND COMBINING THEM INTO A STRAND AND APPLYING AN AQUEOUS SIZE TO THE FILAMENTS AS THEY ARE BEING DRAWN, SAID SIZE CONSISTING ESSENTIALLY OF AN AQUEOUS DISPERSION CONTAINING 2 TO 15 PERCENT BY WEIGHT OF STARCH AND 2 TO 15 PERCENT BY WEIGHT OF A SYNTHETIC RESIN LATEX SELECTED FROM THE GROUP CONSISTING OF: (A) HOMOPOLYMERS OF VINYL ACETATE, METHYL METHACRYLATE, METHYL ACRYLATE, VINYL CHLORIDE, STYRENE, ACRYLONITRILE, CHLOROVINYL ACETATE AND VINYLIDINE CHLORIDE; (B) HOMOPOLYMERIC MIXTURES CONTAINING AT LEAST TWO OF THE HOMOPOLYMERS OF (A); (C) COPOLYMERS OF BUTADIENE WITH A MONOMER SELECTED FROM THE GROUP CONSISTING OF: STYRENE, AND (2) ACRYLONITRILE; (D) POLYMERIC MIXTURES OF A HOMOPOLYMER OF (A) AND A COPOLYMER OF (C); AND (E) POLYMERIC MIXTURES OF A MIXTURE OF HOMOPOLYMERS OF (B) AND A COPOLYMER OF (C), THE COMBINED WEIGHT OF THE STARCH AND LATEX SOLIDS PLUS A SMALL, EFFECTIVE AMOUNT OF AN OIL-FREE, TEXTILE SOFTENER CONSTITUTING ABOUT 13 TO 20 PERCENT BY WEIGHT OF THE SIZE, SAID SOLIDS, SOFTENER AND WATER BEING THE ESSENTIAL INGREDIENTS OF THE SIZE, SAID SIZE HAVING A VISCOSITY OF ABOUT 1 TO 20 CENTIPOISES AT 20*C. 